The leads of semiconductor packages are often solder plated after the package is formed. Many packages are moisture sensitive and cannot be placed in solder flux or other solutions which may be used in the plating process. A wave soldering process is often used in plating leads by moving the device leads across the top of a solder source to coat the leads with solder. This can cause buildup of solder on the leads and also forms solder bridges between the leads.
The use of a soldering bath is described in U.S. Pat. No. 5,161,727. A non-oxidizing atmosphere is used above a solder bath and a conveyor is used to move the parts to be solder plated over the solder bath. This patent defines in particular the housing for providing the non-oxidizing atmosphere above the solder bath.
An apparatus for circulating hot air and a method for wave soldering is defined in U.S. Pat. No. 5,379,943. A fluxed is used to apply the flux to the item to be soldered. High pressure air is circulated within the apparatus and directed against the fluxed surfaces prior to the application of solder.
Additional solder apparatus are described in U.S. Pat. Nos. 5,240,169, 5,228,614 and 5,722,581.